In general, laminated coil components are small in size and light in weight, but have the drawback of a small rated current as compared with wire-wound coil components, because magnetic saturation of the magnetic body decreases the inductance when a large direct-current is applied. Therefore, there is a need for the laminated coil components to be increased in saturated magnetic flux density, in other words, to be improved in DC superimposition characteristics (to achieve stable inductance over a larger direct-current range).
Conventionally, laminated coil components are manufactured in such a way that green sheets of a ferrite material and a conductor paste containing silver are subjected to co-firing in air to form sintered magnetic layers and conductor pattern layers. The laminated coil components obtained by such a manufacturing method also have the problem of having magnetic characteristics of the magnetic body degraded by residual stress generated in the magnetic body due to a difference in coefficient of thermal expansion between the ferrite material and silver.
Under the circumstances, Japanese Patent Application Laid-Open No. 2006-237438 proposes the use of, as a sintering modifier, a conductor paste mixed with SiO2 for covering the silver powder. This sintering modifier is supposed to moderately diffuse into the magnetic body, and make sintering slower near the conductor pattern in the magnetic body than in the other section to make it possible to form a magnetically inactive layer in a gradient fashion, thereby probably making it possible to improve DC superimposition characteristics even over a larger current range. In addition, the sintering modifier is also supposed to be able to prevent the difference in coefficient of thermal expansion between the conductor pattern and the magnetic body from generating residual stress in the magnetic body to degrade magnetic properties.